The present invention relates to a control device for an engine, particularly to a control device for an engine, which adjusts an engine torque according to an operation of an accelerator pedal by a driver.
JP2005-155412A discloses such a kind of art. In JP2005-155412A, a target torque of an engine is set based on a state of an accelerator operated by a driver, and an output torque of the engine is adjusted to reach the target torque by adjusting a throttle opening and/or an ignition timing. Specifically, in this art, an output torque of an engine is adjusted such that a longitudinal acceleration of a vehicle becomes higher as a depressing speed of an accelerator pedal (i.e., a differential value of an accelerator opening) becomes higher, so as to gain an acceleration feeling and reduce vibration of the vehicle in its longitudinal direction.
Meanwhile, when traveling on a rotary, a roundabout (a circular intersection where a plurality of branch roads are connected with a circular passage, which is usually seen in Europe), or a limited speed zone where a vehicle speed is limited to be low, a driver intends to drive at a constant vehicle speed. In this case, the driver tends to operate the accelerator pedal slightly and repeatedly so as to keep the vehicle speed constant. With the conventional art, when the driver operates the accelerator pedal slightly and repeatedly as described above, the acceleration varies according to the variation of the accelerator opening. Therefore, it is difficult to keep the vehicle speed constant. In other words, it is difficult to control the vehicle to maintain the constant vehicle speed. Especially, with the conventional art, since the way the acceleration changes with respect to the change of the accelerator opening varies depending on a current operating state (e.g., vehicle speed and gear position) of the vehicle, it is further difficult to keep the vehicle speed constant.